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MCBG TEST 2!!! > 9-2 Intracell Sorting > Flashcards

9-2 Intracell Sorting Flashcards

0
Q

Golgi Apparatus the “____”

A

Golgi Appartus/the “pancakes” function to sort proteins and work within the exocytic network

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1
Q
  • Nuclear membranes are ______ with the Endoplasmic Reticulum
    2. What size is the Nucleus in comparison to other organelles?
A

So….Nuclear membranes are CONTINUOUS with the ER organelle!

2.Nucleus is PROMINENT making up of about 10% entire cell volume

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2
Q

ENDosome

A

Eukaryotic organelle that provides a place for material to be sorted BEFORE IT’S SENT TO LYSOSOME FOR THE KILLING!

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3
Q

The ____ ____ allows proteins to target a specific location within a cell. Where can this actually be found within the protein?

A

The SORTING SIGNAL (peptide sequence) of a protein allows it to target a specific organelle/location

Sorting Signal is found WITHIN THE AMINO ACID SEQ. of the protein

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4
Q

What’s the difference between a Signal Peptide vs. Signal Patch

A

Signal Peptide=Linear sequences located at the end of a protein usually

**Signal PATCH= FORMED AFTER PROTEIN FOLDING OCCURS and all sites inteRACT

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5
Q

What Sorting Signal Peptide Sequence do Proteins headed to the
“ENDOPLASMIC RETICULUM/ER” have?

A

ER Protein signal peptides haveDense (20-30 AA) HYDROPHOBIC CORE!

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6
Q

What Sorting Signal Peptide Sequence do Proteins headed to the
“Mitochondria” have?

A

Mitochondria signals are [N-terminal amphipathic AlpHA HeliCEs] with hydrophobic AA spaced ~every 4 AA

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7
Q

What Sorting Signal Peptide Sequence do Proteins destined for
“Nuclear Import” have?

A

Nuclear Import signals are very Basic

“Nuclear importing is very BASIC”

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8
Q

What Sorting Signal Peptide Sequence do Proteins destined for
“Nuclear EXPORT” have?

A

Nuclear EXPORT signals are LEUCINE-RICH

“They Exported Leucy a long time ago”

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9
Q

What 2 Sorting Signal Peptide Sequence do Proteins destined for
“Peroxisomes” have? [2]

A

1.Peroxisomal signals are a (c-terminal*SKL-COOH) sequences
[Serine,Lysine,Leucine-COOH]

  1. (N-terminal) Arg-Leu-X-X-X-X-His-Leu
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10
Q

What happens if a signal directing peptide is removed from 1 factor and then placed on another

A

That signal would make the NEW protein go to whatever Target the old protein was supposed to go

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11
Q

Which organelle would a protein tagged with a “KDEL” signal peptide go?

A

KDEL Peptide Sequence= STAY in LUMEN of the ER

“KDEL wanted to stay in the lumen of the ER”

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12
Q

1) How many proteins can pass thru the nuclear pore at one time and which direction do they go?
2) What’s the restriction to this? [3]
3) How many nucleoporins does 1 nucleus have?

A

1)500 proteins can pass through the nuclear pore/second bidirectionally using cytosolic&nuclear fibrils—WITHOUT TRAFFIC JAMS!

2)Nuclear Pores only permeable to molecules LESS than 60 kDA.
Lrger than tht requires
-active energy gate transport,
-Nuclear localization signal/Import signal for import
-and Nuclear export signal for export

3 *Nucleus has 4000 nuclear pores/cell

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13
Q

What are some organelles that import proteins from the cytosol right after Protein synthesis (post-tl) [4]

A
  1. Nucleus (via nuclear pores)
  2. Mitochondria (TOM and TIM)
  3. Peroxisomes (destination signal is on C-terminus end of Protein)
  4. ER (via Sec61 protein to get in and SRP to bind to ER membrane)
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14
Q

A)) Describe the complete Process of Nuclear IMPORTING! [4]

B)Which Ran(s) are the highest concentration INSIDE NUCLEUS?

A

A))1-cytosolic Protein Cargo[PC] w/Nuclear Import Signal in it binds to importin receptor–>IMPORTIN-COMPLEX!
2- IMPORTIN-C binds to Nuclear Pore and is shuffled into nucleus

3) Once in Nucleus, RanGDP is Given a Phosphate by RanGEF
- ->RanGTP –>which binds to IMPORTIN-COMPLEX & stimulates Protein CArgo to detach from Importin receptor
4) RanGTP + Importin receptor travels to cytosol to restart cycle

B== RanGEF and R-GTP are the HIGHEST CONCENTRATION INSIDE NUCLEUS! “GEF liked to stay INSIDE the Nucleus w/GTP a lot”

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15
Q

A)) Describe the complete Process of Nuclear ExPorTing
“Get it Outta this NucleUS” [4]

B)Which Ran(s) are highest concentration Outside the nucleus?

A

A) 1-[R-GTP] inside nucleus promotes Protein cargo with Nuclear EXPORT signal to bind to export receptor–>EXPORTANT-COMPLEX

2) Ternary EXC binds to Nuclear Pore fibrils and travels thru pores outside to cytosol
3) Once in cytoplasm RanGAP hydrolyzes bound R-GTP->R-GDP which will DETACH Protein Cargo from Exportant in cytosol

4)Exportant Receptor and GDP separately return to nucleus for recycling

B==B== RanGAP and R-GdP are HIGHEST CONCENTRATION Outside nucleus!

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16
Q

How is Nuclear Import/uptake related to NF-KB and I-Kappa B

A

When I-Kappa B is phorsphorylated it is no longer able to inhibit
NF-KB(stimulates cell growth/cancer)–>NF-KB goes and gains a nuclear import signal so it can translocate to nucleus=INC cell growth/possible Cancer :-(

17
Q

What happens to Nuclear Import/Localization signals when the nucleus breaks down for mitosis?

A

AFter Mitosis, Nuclear Import signals on proteins STAYS PUT so that nuclear proteins can go back to their respective nuclear or cytosol “homes” after nucleus reforms

18
Q

A–What are the 4 compartments of the Mitochondrion?

B–Where are the Mitochondria Proteins made??

A
  1. Matrix
  2. INNER Membrane
  3. intermembrane space
  4. OUTER Membrane

B–Mitochondria Proteins encoded by nuclear genome and made in Cytosol –>then sent to Mitochondria

19
Q

What are the Main Steps to getting a protein INSIDE the Mitochondria from cytosol?? [5]

A

After Translation……..

1) AA Signal Peptide seq. on Target Protein directs it to mitochondrias TOM[Translocase of outer membrane] where it binds
2) Trget Protein then “pushed” thru OUTER TOM by chaperone HSP70 and released into intermembrane space after HSP70 ATP hydrolysis

3) unfolded Trget Protein {now in intermembrane space} thens electrophorese into matrix space [due to electrochemcial potential across inner membrane] and finally…
4) Chaperone HSP70 this time “pulls” protein thru TIM[Translocase of inner membrane] and releases it inside mitochondria after HSP70 ATP hydrolysis again –>Woo!
5) Signal peptide seq. IS CLEAVED OFF IN MITOCHONDRIA (opposite of nucleus peptide signals which stays put)

20
Q

What does HSP60 Mitochondria Chaperone do?

A

HSP60(Heat Shock Protein) can act as a “GroEL”–>which isolates misfolded proteins using a GroES capped “microwave” –>until protein fixes the misfold itself!

20
Q

How does Mitochondria Chaperone HSP70 (also used in________) fix misfolded proteins?

A

HSP70(also used to pull and push target proteins inside Mitochondria) fixes misfolded proteins by binding to hydrophobic domains of the bad protein until it folds correctly. Then it releases it “claws”

21
Q

Name 3 important functions of the Peroxisome

A
  1. OXIDATION OF both Long Fatty Acid Chains and EtOH
  2. Decomposition of Hydrogen Peroxide
  3. Synthesis of plasmalogens (myeline membrane lipids)
22
Q

What are 3 MAIN differences between Mitochondria and Peroxisomes?

A

1st: MitoChon do MOST of the oxidation w/oxidative phosphorylation
2nd: Peroxisomes use CATALASE redox rxn, detoxifies poisons and use beta-oxidation of fats to make acetyl CoA

3rd: Peroxisomes LACK inner cristae and have a DENSE CORE!

23
Q

Function of the ROUGH Endoplasmic Reticulum

A

Has bound ribosomes and it performs HALF of all protein synthesis(secreted and membrane proteins).

24
Q

Function of the smoooooth Endoplasmic Reticulum [2]

A

smoooooth ER=1.lipid biogenesis and

  1. lipid-soluble drug detoxification by converting into water soluble
    - ->will urine out
25
Q

Function of transitional Endoplasmic Reticulum

A

(Similar to smooooth ER) Transitional ER=where ER cargo vesicles bud off to head to other destinations

26
Q

What does cotranslational transport mean?

A

Soomething Endoplasmic Reticulum does=proteins (SECRETORY and TRANSMEMBRANE types) are MADE on ER membrane while simultaneously being inserted INTO the membrane and pushed inside ER

27
Q

WWhat is the ultimate destination of proteins inserted into the Endoplasmic Reticulum?

A

They become Secretory proteins OR Transmembrane Proteins

28
Q

General Steps of Co-Translation for Endoplasmic Reticulum [4]

A

dense 20-30 AA hydrophobic signal peptide binds to SRP which temporarily stops free translation elongation
2-SRP binds to SRP receptor which brings protein to ER membrane

3) Transltn continues when ribosome is positioned above the Sec61 transmembrane pore
4) Protein is driven into ER lumen PURELY AS A RESULT OF TRANSLATION ITSELF and then ribosome dislocates when done

29
Q

Most proteins of the ER insert _____. But a small group of proteins spontaneously insert _____

A

MOST ER proteins insert co-translationally

…BUT small group of proteins spontaneously insert POSTTranslation w/their hydrophobic parts of protein embedded naturally into hydrophobic area of ER membrane

30
Q

Transmembrane proteins contain a ______sequences that ____protein into membranes. These seq. are made of —-
2)How does this work?

3)How do Transmembrane proteins fix their amino end vs. Carboxyterminal end inside the ER lumeN?

A

1) Transmembrane proteins contain a STOP-TRANSFER sequence that ANCHORS protein into membranes. (These seq. areas are composed of Charged AA that flank hydrophobic stretches )
2) after hitting a stop transfer seq. ribosome finishes transltion cytosolically and stop-span will come out stuck in the membrane after Sec61 pliers finally releases its grip
3) Strt/Stop transfer seq. can allow membrane proteins to be N-terminal or C-terminally fixed using [[[STITCHING of a nascent linear protein chain in 1 or the other direction thru Sec61 pliers ]]]

31
Q

How are multipass membrane proteins (such as the _______) inserted into the membrane?

A

Multipass membranes(ex. 7-transmembrane Protein) has MORE THAN 1 START AND STOP TRANSFER SEQUENCE –>which means it’s Stitching will STOP multiple times within a membrane

32
Q

Why is the 7-transmembrane protein multipass important?

A

Is a big starting point for MANY signal transduction processes (including signals of sight/taste/smell)

33
Q

WHAT happens to Proteins retained in the ER for folding but that FAIL to fold??

A

Those proteins are Degraded!

34
Q

1)Describe the co-translational attachment of
mannose-oligosaccharide to Asparagine N-linked glycoproteins—>
“N-glycosylation”[MORE COMMON]

2)How is this related to transmembrane & secreted proteins?

A

N-glycosylation happens when dolichol lipid substrate “lures” the buildup of mannose-oligosaccharide sugar which is then COVALENTLY attached to Asparagine residues in a
[ Asn-X-(Thr/Ser) ] pattern.

2)*Most transmembrane & secreted proteins are GLYCOproteins becuz of this..

35
Q

What are the purposes of N-Linked Glycoprotein/Glycan structures?? [4]

A
  1. Controls ER protein folding
  2. Protects underlying protein from proteases or antibody attcks
  3. Adds hydrodynamic volume
  4. operates as sorting signal and “lectin” communication tool
36
Q

Describe briefly [O-linked Glycosylation] of ______ residues during ER co-translational modification phase

2)What’s an example of an O-linked glycosylated protein? What is O-linked glycosylation purpose?

A

least common glycosylation– involving sugar COVALENT ATTACHMENT TO OXYGEN of …. Serine or Threonine AA=glycans
(vs. normal attachment to Asparagine)

2)Ex. O-linked = “Mucins”–>glycans on mucins absorb water &create gel-like mucus to prtect under cell from dessication & pathogens within lungs or intestine

37
Q

Explain the MISFOLDED Protein Response system of the ER [5]

A
  • Abundant proteins may cause lots of misfolding->
  • ER “sensors”(like IRE) picks this up and dimerizes to form ribonuclease.–>
  • RiboNuclse splices pre-mRNA > mRNA that encodes for gene ER regulatory protein (which travels to nucleus). —–>
  • Reg. protein enters nucleus to drive tx of ER chaperone genes

*——–>which r then trnslted INTO THE ER to fix misfolded proteins!

38
Q

What are possible consequences for cells exposed to prolllongged exposure to MISFOLDED/unfolded ER proteins?

A

Ex. Type 2 DM= cells will suffer and eventually undergo APOPTOSIS

39
Q

What is also unique about the Protein Misfolded feedback loom from ER?

A

*misfolded protein feedback look from ER nucleus also plays big role in controlling cholesterol levels (since cholesterol is made in the ER).

** ER enzymes tht help w/cholesterol synthesis are under control of ER/Golgi-located sensors and ER enzymes use the Nucleus to regulate expression of sterol biosynthetic genes

MCBG TEST 2!!! (13 decks)

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